Abstract: A van der Waals capacitor and a qubit constructed with such a capacitor. In some embodiments, the capacitor includes a first conductive layer; an insulating layer, on the first conductive layer; and a second conductive layer on the insulating layer. The first conductive layer may be composed of one or more layers of a first van der Waals material, the insulating layer may be composed of one or more layers of a second van der Waals material, and the second conductive layer may be composed of one or more layers of a third van der Waals material.

Abstract: An amplifier. In some embodiments, the amplifier includes a resonant circuit having a resonant frequency, a pump input, a signal input, and a signal output. The resonant circuit may include a Josephson junction connected to the pump input, the Josephson junction being a superconducting-normal-superconducting junction having two superconducting terminals and being configured to adjust the resonant frequency of the resonant circuit based on a signal received at the pump input.

Abstract: Techniques for machine learning assisted qubit state readout are disclosed. A system a set of training data that describes states of multiple qubits, and trains a neural network to determine qubit states based on the set of training data. The system obtains one or more unlabeled qubit signals, and determines one or more states corresponding to the unlabeled qubit signal(s), using the neural network. The unlabeled qubit signal(s) may include one or more multiplexed qubit signals, and the state(s) corresponding to the unlabeled qubit signal(s) may include one or more multi-qubit states based on the multiplexed qubit signal(s).

Abstract: A microwave switch. In some embodiments, the microwave switch includes a substrate, a signal conductor, a first ground conductor, on a first side of the signal conductor, and a second ground conductor, on a second side of the signal conductor. The signal conductor, the first ground conductor, and the second ground conductor may be planar conductors on a planar top surface of the substrate. The signal conductor may have a first portion composed of a superconducting material, and a second portion having a reduced cross section, a cross-sectional area of the second portion being less than 120 nm.

Abstract: A transistor. In some embodiments, the transistor includes a first superconducting source-drain, a second superconducting source-drain, a graphene channel including at least a portion of a graphene sheet, and a conductive gate. The first superconducting source-drain, the second superconducting source-drain, and the graphene channel together form a Josephson junction having a critical current. The graphene channel forms a current path between the first superconducting source-drain and the second superconducting source-drain. The conductive gate is configured, upon application of a electric field across the conductive gate and the graphene channel by applying a voltage, to modify the critical current.

Abstract: An amplifier. In some embodiments, the amplifier includes a resonant circuit having a resonant frequency, a pump input, a signal input, and a signal output. The resonant circuit may include a Josephson junction connected to the pump input, the Josephson junction being a superconducting-normal-superconducting junction having two superconducting terminals and being configured to adjust the resonant frequency of the resonant circuit based on a signal received at the pump input.

Abstract: A microwave switch. In some embodiments, the microwave switch includes a substrate, a signal conductor, a first ground conductor, on a first side of the signal conductor, and a second ground conductor, on a second side of the signal conductor. The signal conductor, the first ground conductor, and the second ground conductor may be planar conductors on a planar top surface of the substrate. The signal conductor may have a first portion composed of a superconducting material, and a second portion having a reduced cross section, a cross-sectional area of the second portion being less than 120 nm.

Abstract: A photon detector including a graphene-insulating-superconducting junction configured as a temperature sensor. Photons are absorbed by the graphene sheet of the graphene-insulating-superconducting junction, each absorbed photon causing a temporary increase in the temperature of the graphene sheet, and a corresponding change in the differential impedance of the graphene-insulating-superconducting junction. The graphene-insulating-superconducting junction is part of a resonant circuit connected as a shunt load between a radio frequency input transmission line and a radio frequency output transmission line. The transmission S-parameter from input to output is affected by the impedance of the resonant circuit which in turn is affected by the differential impedance of the graphene-insulating-superconducting junction, and therefore by the temperature of the graphene sheet.

Abstract: A transistor. In some embodiments, the transistor includes a first superconducting source-drain, a second superconducting source-drain, a graphene channel including at least a portion of a graphene sheet, and a conductive gate. The first superconducting source-drain, the second superconducting source-drain, and the graphene channel together form a Josephson junction having a critical current. The graphene channel forms a current path between the first superconducting source-drain and the second superconducting source-drain. The conductive gate is configured, upon application of a electric field across the conductive gate and the graphene channel by applying a voltage, to modify the critical current.

Abstract: A photon detector including a graphene-insulating-superconducting junction configured as a temperature sensor. Photons are absorbed by the graphene sheet of the graphene-insulating-superconducting junction, each absorbed photon causing a temporary increase in the temperature of the graphene sheet, and a corresponding change in the differential impedance of the graphene-insulating-superconducting junction. The graphene-insulating-superconducting junction is part of a resonant circuit connected as a shunt load between a radio frequency input transmission line and a radio frequency output transmission line. The transmission S-parameter from input to output is affected by the impedance of the resonant circuit which in turn is affected by the differential impedance of the graphene-insulating-superconducting junction, and therefore by the temperature of the graphene sheet.

Abstract: A detector for detecting single photons of infrared radiation or longer wavelength electromagnetic radiation. In one embodiment a waveguide configured to transmit infrared radiation is arranged to be adjacent a graphene sheet and configured so that evanescent waves from the waveguide overlap the graphene sheet. In other embodiments a transmission line or antenna is coupled to the graphene sheet and guides longer-wavelength photons to the graphene sheet. A photon absorbed by the graphene sheet heats the graphene sheet. Part of the graphene sheet is part of the Josephson junction as the weak link, and a constant bias current is driven through the Josephson junction; an increase in the temperature of the graphene sheet results in a decrease in the critical current of the Josephson junction and a voltage pulse in the voltage across the Josephson junction. The voltage pulse is detected by the pulse detector.

Abstract: A detector for detecting single photons of infrared radiation or longer wavelength electromagnetic radiation. In one embodiment a waveguide configured to transmit infrared radiation is arranged to be adjacent a graphene sheet and configured so that evanescent waves from the waveguide overlap the graphene sheet. In other embodiments a transmission line or antenna is coupled to the graphene sheet and guides longer-wavelength photons to the graphene sheet. A photon absorbed by the graphene sheet heats the graphene sheet. Part of the graphene sheet is part of the Josephson junction as the weak link, and a constant bias current is driven through the Josephson junction; an increase in the temperature of the graphene sheet results in a decrease in the critical current of the Josephson junction and a voltage pulse in the voltage across the Josephson junction. The voltage pulse is detected by the pulse detector.

Abstract: A magnetic random access memory (MRAM) array including: a plurality of MRAM cells arranged in an array configuration, each comprising a first type nTron and a magnetic memory element; a wordline select circuit comprising of a second type nTron to drive a plurality of parallel wordlines; and a plurality of bitline select circuits, each comprising of said second type nTron for writing to and reading from a column of memory cells in the array and each capable of selecting a single MRAM cell for a memory read or write operation, wherein the second nTron has a higher current drive than the first nTron.

Abstract: A detector for detecting single photons of infrared radiation. In one embodiment a waveguide configured to transmit infrared radiation is arranged to be adjacent a graphene sheet and configured so that evanescent waves from the waveguide overlap the graphene sheet. In some embodiments the waveguide is omitted and infrared light propagating in free space illuminates the graphene sheet directly. A photon absorbed by the graphene sheet from the evanescent waves heats the graphene sheet. The graphene sheet is coupled to the weak link of a Josephson junction, and a constant bias current is driven through the Josephson junction, so that an increase in the temperature of the graphene sheet results in a decrease in the critical current of the Josephson junction and a voltage pulse in the voltage across the Josephson junction. The voltage pulse is detected by the pulse detector.

Abstract: A detector for detecting single photons of infrared radiation or longer wavelength electromagnetic radiation. In one embodiment a waveguide configured to transmit infrared radiation is arranged to be adjacent a graphene sheet and configured so that evanescent waves from the waveguide overlap the graphene sheet. In other embodiments a transmission line or antenna is coupled to the graphene sheet and guides longer-wavelength photons to the graphene sheet. A photon absorbed by the graphene sheet heats the graphene sheet. Part of the graphene sheet is part of the Josephson junction as the weak link, and a constant bias current is driven through the Josephson junction; an increase in the temperature of the graphene sheet results in a decrease in the critical current of the Josephson junction and a voltage pulse in the voltage across the Josephson junction. The voltage pulse is detected by the pulse detector.

Abstract: A magnetic random access memory (MRAM) array including: a plurality of MRAM cells arranged in an array configuration, each comprising a first type nTron and a magnetic memory element; a wordline select circuit comprising of a second type nTron to drive a plurality of parallel wordlines; and a plurality of bitline select circuits, each comprising of said second type nTron for writing to and reading from a column of memory cells in the array and each capable of selecting a single MRAM cell for a memory read or write operation, wherein the second nTron has a higher current drive than the first nTron.

Abstract: A detector for detecting single photons of infrared radiation. In one embodiment a waveguide configured to transmit infrared radiation is arranged to be adjacent a graphene sheet and configured so that evanescent waves from the waveguide overlap the graphene sheet. An infrared photon absorbed by the graphene sheet from the evanescent waves heats the graphene sheet. The graphene sheet is coupled to the weak link of a Josephson junction, and a constant bias current is driven through the Josephson junction, so that an increase in the temperature of the graphene sheet results in a decrease in the critical current of the Josephson junction and a voltage pulse in the voltage across the Josephson junction. The voltage pulse is detected by the pulse detector.

Abstract: A magnetic random access memory (MRAM) array including: a plurality of MRAM cells arranged in an array configuration, each comprising a first type nTron and a magnetic memory element; a wordline select circuit comprising of a second type nTron to drive a plurality of parallel wordlines; and a plurality of bitline select circuits, each comprising of said second type nTron for writing to and reading from a column of memory cells in the array and each capable of selecting a single MRAM cell for a memory read or write operation, wherein the second nTron has a higher current drive than the first nTron.

Abstract: A detector for detecting single photons of infrared radiation. In one embodiment a waveguide configured to transmit infrared radiation is arranged to be adjacent a graphene sheet and configured so that evanescent waves from the waveguide overlap the graphene sheet. An infrared photon absorbed by the graphene sheet from the evanescent waves heats the graphene sheet. The graphene sheet is coupled to the weak link of a Josephson junction, and a constant bias current is driven through the Josephson junction, so that an increase in the temperature of the graphene sheet results in a decrease in the critical current of the Josephson junction and a voltage pulse in the voltage across the Josephson junction. The voltage pulse is detected by the pulse detector.

Abstract: A detector for detecting single photons of infrared radiation. In one embodiment a waveguide configured to transmit infrared radiation is arranged to be adjacent a graphene sheet and configured so that evanescent waves from the waveguide overlap the graphene sheet. In some embodiments the waveguide is omitted and infrared light propagating in free space illuminates the graphene sheet directly. A photon absorbed by the graphene sheet from the evanescent waves heats the graphene sheet. The graphene sheet is coupled to the weak link of a Josephson junction, and a constant bias current is driven through the Josephson junction, so that an increase in the temperature of the graphene sheet results in a decrease in the critical current of the Josephson junction and a voltage pulse in the voltage across the Josephson junction. The voltage pulse is detected by the pulse detector.